Selection mechanism for typewriter



Sept. 22, 1959 J E. HICKERSON 2,905,302

SELECTION MECHANISM FOR TYPEWRITER Filed Aug. 28, 1956 2 Sheets-Sheet 1INKENTOR JOHN E. HICKERSON ATTORNEY Sept. 22, 1 5 J. E. HICKERSONSELECTION MECHANISM FOR TYPEWRITER Filed Aug 28, 1956 2 Sheets-Sheet 2SELECTION MECHANISM FOR TYPEWRITER John E. Hickerson, Wappingers Falls,N.Y., assignor to International Business Machines Corporation, New York,N.Y., a corporation of New York Application August 28, 1956, Serial No.606,600

7 Claims. (Cl. 197-52) This invention relates to typewriters, and moreparticularly to a mechanism for selectively positioning a single elementprinting head with respect to the platen of a typewriter.

The principal object of the present invention is to provide a low costimproved selecting mechanism for positioning a single element printinghead which is capable of rapid and reliable operation over long periodsof time.

When using purely mechanical means, the maximum speed of selecting thecharacter may be limited by the time taken by the machine to completethe manipulation of the printing head to move the character to areference position, and not by the speed of the operator. It is anobject of the present invention to provide an improved form ofelectromechanical device for positioning the printing head, in which theoperating speed is considerably increased, so that the machine speed isnot the limiting factor.

It is possible that the operator may depress a second key lever beforethe character selected by the first key lever has printed; accordingly,it is another object to provide a means to prevent the manipulation ofthe printing head by operation of a second key lever during theselecting and printing time resulting from the depression of the firstkey lever.

Another object of the invention is to provide for only one displacementof the single element printing head for each operation of a key lever.

Further, an object is to provide for storage of a subsequent characterduring the time taken to manuipulate the printing head and print acharacter.

It is a still further object of this invention to provide a selectingmechanism wherein a uniform key lever force triggers a power-operateddevice which completes the manipulation of the selecting process withoutfurther manual force.

In the preferred form of the invention, the single element printing headis tilted and rotated in response to depression of key levers, each keylever being assigned to a character on the printing head. Depression ofa selected key lever causes an interposer to engage a power bail andclose an electrical circuit. The electrical circuit supplies power tothe bail which drives the interposer against angular recesses in a pairof bars with the result that the bars are displaced laterally by theamount of movement required to both tilt and rotate the printing head toposition the character that corresponds to the actuated key lever. Onebar controls a tilt system comprising pulleys and a tape to tilt theprinting head; another bar controls a rotation system comprising pulleysand a tape to rotate the printing head. After the selected character ispositioned with respect to a platen, a bail drives the printing head toengagement with the paper and platen, and the printing head is moved tothe next letter space by an electromechanical device.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

2,905,32 Patented Sept. 22, 1959 Fig. 1 is a perspective drawing of theselecting mechanism including the single element printing head and thetapes and pulleys for its control.

Fig. 2 is a top plan view of the tape control system for positioning thecharacter on the single element printing head.

Fig. 3 is a section of the single element printing head through theplane 33 of Fig. 1.

Fig. 4 is an elevation showing the selecting mechanism actuatingelements.

Fig. 5 is an elevation showing a return mechanism for the tape controlsystem.

In Fig. 1, there is shown a key lever 10, which is only one of aplurality of key levers, each having a key button. The key levers extendover a plurality of interposers 11, each key lever extending over itsrespective interposer. The key lever 10 is pivotably mounted on a fixedrod 12 common to all key levers 10. Coupled to the key lever 10 in anysuitable manner, such as by a stud 13, is a bell crank 14 with a lipupon which the key lever 10 rests. By means of a spring 15, the bellcrank 14 is normally held in resilient engagement with the key lever 10,and the key lever 10 is held in its uppermost and rest position againsta stop not shown. The bell crank 14 impinges upon the lip of aninterposer 11 when the key lever 10 is depressed. The interposer 11 isslidably mounted and loosely pivoted on a fixed rod 16, which is commonto all interposers, and is biased upwardly against a stop not shown andforwardly by a spring 17. Mounted directly beneath the interposer 11 andthe remainder of the interposers and at right angles to them is a rod 18which is forced down vertically when the interposer 11 is pivoted by thebell crank 14.

The rod 18 is connected to a bell crank 19, which pivots about a fixedrod 20 and both rods 18 and 20 extend the width of the mechanism and areconnected to another bell crank at the opposite end of the mechanism notshown. When the rod 18 is moved down by the interposer 11, the bellcrank 19 is caused to pivot counterclockwise about the axis of the rod20. Pivotably connected to the bell crank 19 by a stud 21 is an arm 22,which has a shoulder suitably constructed to operate against anactuating member of a contact assembly 23, which is normally open. Aspring 24 couples the bell crank 19 and the arm 22 together and normallyholds the arm 22 against the actuating member of the contact assembly 23without closing said contacts.

When the arm 22 is swung counterclockwise by the bell crank 19, thecontact assembly 23 closes thereby actuating a solenoid 25 byapplication of a DC. voltage 26 to its coil terminals. The solenoid 25attracts an armature 27 and pivots a bell crank 23 about a stud 29.Coupled to the bell crank 23 is a rod 30, the other end of which isconnected to an activating bail 31. The activating bail 31 is pivotallyconnected at its ends and extends beneath the interposer 11 and allother interposers. The energization and subsequent de-energization ofthe solenoid 25 will impart reciprocating motion to the activating bail31 via the bell crank 23 and the rod 30. On its initial stroke theactivating bail 31 engages the shoulder of the interposer 11 when saidinterposer is pivoted. A differential bar 32 has angular recessescutalong its length with each recess of different degree of inclinationopposite one of the interposers 11. The interposer 11 is engagedperpendicularly with the bar 32 by the activating bail 31 which causesthe bar 32 to move laterally to the right by camming action at itsengaging surface. Since the angle of the recess in the bar 32 determinesthe amount of lateral movement imparted to said bar for each particularcharacter to be printed, the angle of cut must necessarily differaccording to the desired movement of the printing head to position aparticular 3 character with respect to the reference point. It followsthat the differential bar 32, as well as a similarly constructeddifferential bar 33 may move laterally to the right or left by apredetermined amount depending upon ,the engageable cam surface oppositethe particular interposer 11. The bar 32 is pivotally coupled to an arm34 and an arm 35 at its ends by studs 36 and 37 respectively. Further,thearm 34 is pivotally connected to a fixed stud 38, and the arm 35 ispivotally connected to a fixed stud 39. At the same time that theinterposer 11 en gages the bar 32, the interposer 11 engages the bar 33,

which is located directly beneath bar 32. Interposer 11 causes the bar33 to move to the right laterally by camming action at the angularengaging surface of the bar 33. The bar 33 is pivotally coupled at itsends to an v arm 41 and an arm 42 by studs 43 and 44 respectively.

With this arrangement of parts, lateral movement of the bars, 32 and 33causes the arms 34 and 35 and the arms 41 and 42 to pivot about thefixed pins 38 and 39 respectively. A pulley 50 is rotatably coupled by apin 51 to the arm 34 at the arms end toward the printing head; likewise,a pulley 52 is coupled to the ann 35 by a pin 53. The tilt controlsystem is composed of the pulleys 50 and 52, a double-track pulley 54, atape 56, and a slidable member 58. As shown in Fig. 2,

the tape is strung in the following manner: From the notch in the uppertrack of the pulley 4, around the track in the pulley 54 on the sidenearest pulley 52, around the pulley 50, through and fixed to theslidable memher 58, around the pulley 52, around the lower track of thepulley 54 on the side nearest pulley 50, and to the notch in the lowertrack of pulley 54. The slidable member 58 remains fixed with respect toa rod 59 during the selecting motion of the tape 56 and is moved in theletter space operation to be described later. With this arrangement ofparts, the lateral movement of the centers of the pulleys 50 and 52 istranslated to the circular movement of the pulley 54 through the tape56. Movement of the pulley 54 tilts the printing head (in a manner to bedescribed later) from its vertical axis by a predetermined amount toselect the proper line of type about the surface of the printing head.

In Figure l, a rotation pulley 60 is rotatably coupled by a pin to thearm 41; likewise, the pulley 62 is coupled to the arm 35 by a pin. Therotation system is identical in construction and operation to the tiltcontrol system and is composed of the pulleys 60 and 62, a double trackpulley 64, a tape 66, and the slidable member 58. The tape cooperateswith these parts in the same way that the tape 56 acts in the tiltcontrol system so that the lateral movement of the centers of thepulleys 60 and 62 is translated to circular movement of the pulley 64.Thus, the printing head is caused to rotate about its vertical axis by apredetermined amount related to the particular key lever depressed.

The printing head, although forming no part of the invention, will beexplained for the purpose of clarity. With reference to copendingapplication Serial Number 547,481 filed November 17, 1955, whichapplication is assigned to a common assignee, the single elementprinting head is in the form of a truncated sphere or ball withcharacters arranged on the face of the printing element (in rows andcolumns) with only one character in printing position at a time. Onecharacter at a time is moved to a single printing position by rotatingand tilting the printing element.

In Fig. 3, a supporting tube 70 carries an integral base member yoke 71having arms 72 and 73. A pivot pin 74 is supported in the upper end ofthe arms 72 and 73. A hollow tilt shaft 75 which carries a tilt gear 76is passed axially through post 70. The tilt gear 76 is engageable with acomplementary tilt gear sector 77 which is an integral portion of a tiltmember or supporting frame 78 that is supported for tilting movementabout the tilt pin 74. With this arrangement of parts the turning of thetilt shaft 75 causes pivoting of the tilt gear sector 77 to rock thesupporting frame 78 about the tilt pin 74 and tilts a truncated shell 80on which the characters are arranged.

A turn shaft 81 is supported coaxially of supporting tube 70 and lieswithin the tilt shaft 75. A turn gear 82 is mounted on the upper end ofturn shaft 81 to mesh with an idler 83 supported for free rotation aboutthe pivot pin 74. The idler 83 in turn is meshed with a turn pinion 84.The truncated spherical shell 80 having print characters arranged on theperipheral surface thereof is slid over cylinder 86 which has a bottomflange 87. With this arrangement of parts, the turning of the shaft 81causes turning of gear 82, the idler 83, and the consequential rotationof the bevel gear 84. This action causes rotation of the truncatedspherical shell 80.

In Fig. 1, it can now be seen that bar 32 causes movement of pulleys 50and 52 which in turn move the tape 56 to rotate the pulley 54 whichtilts the printing head 80 and that bar 33 causes movement of pulleys 60and 62 causing tape 66 to rotate pulley 64 which rotates the printinghead 80. Therefore, the independent and cooperative movement of the pairof bars 32 and 33 manipulate the proper character on the spherical shell80 to place the character at the single printing position with respectto a platen 89.

Near the limit of counter-clockwise travel of the activating bail 31,said bail 31 engages a normally open contact assembly 90 at an insulatedportion thereon and closes said contact, completing a circuit composedof a DC. voltage source 91 and a solenoid 92 in series connection withelectric wire. An armature 94 is disposed within the solenoid coil 92and is pivotably connected to an arm 96 by a rivet 97. The arm 96 isfixed to a power bar 99 adapted for rotational movement. The power bar99 has a lip extending beneath a pivotably mounted bracket 100 within aframe 102, and said bracket 100 has an arm above the power bar 99. Aspring 103 normally holds the bracket 100 in a substantially horizontalposition against a stop 104. When the solenoid 92 is energized, thearmature 94 is attracted coaxially with said solenoid coil 92, the arm96 is pivoted clockwise, and the lip on the power bar 99 is moved upwardcausing the bracket 100 to pivot within the frame 102. The supportingtube 70 of the printing head assembly is contained within the collarportion of the bracket 100. When the bracket 100 is pivoted by the powerbar 99, the printing shell 80 is driven into engagement with the platen89. When the contact 23 is opened as particularly described-hereafterand the activating bail 31 pivots clockwise, the contact 90 opens andde-energizes the solenoid 92. The spring 103 acting upon the bracket 100restores the printing head, and the bracket 100 causes the solenoidarmature 94 to return from its attracted position.

At the limit of counter-clockwise travel of the activating bail 31, astud on the activating bail 31 engages the lever arm 22 pressing itdownward and causing the shoulder of the arm 22 to become disengagedfrom the acti vating member of the contact assembly 23 opening saidcontact 23 and removing the voltage from the solenoid 27. The activatingbail 31 is returned clockwise to its normal and disengaged position bythe return stroke of hell crank 28 urged by a spring 49, and theinterposer 11 is returned by the spring 17. If. the key lever 10 hasremained depressed, the lip of the interposer 11 engages the bell crank14 and pivots the bell crank 14 counter-clockwise about the stud 13causing the lip of the bell crank 14 to move down and away from the keylever 10. The printing cycle cannot be repeated until the key lever 10is returned to normal since the bell crank 14 is held in front of thelip on the interposer 11. Thus, the bell crank 14 is prevented fromacting upon the top of the lip on the interposer 11 and causing it toengage the rod 18, which normally would close the contact 23. When thekey lever has been released, the bell crank 14 is restored to restposition by the urging of the spring 15.

To effect leter spacing, the frame 102 carrying the printing head iscaused to move laterally adjacent the fixed platen 89. The frame 102 isslidably supported by a rod 105 and a rod 106, both suitably fixed attheir ends. The rods 105 and 106 permit lateral movement of the frame102 in response to movement of a tape 111. A pulley 112 is rotatablycoupled to the base of the machine by a fixed pin 113, and the followingpulleys are connected to the base in the same manner; pulley 114 and pin115, pulley 116 and pin 117, pulley 118 and pin 119, pulley 121 and pin122, pulley i124 and pin 12. 5, and pulley 126 and pin 127. The tape 111is fixed to the printing head frame 102, engages the tracks of thepulleys 112, 114, 124 and 126, is fixed to a notch in a rotatable pulley126, engages pulleys 121, 118 and 116, and is fixed to the frame 102.With this arrangement of parts, movement of pulley 126 will causecorresponding movement of the frame 102. Integrally attached to thepulley 126 is a gear 128, which accommodates a spring 129 within arecessed portion of the gear 128. The spring 129 couples the gear 128 tothe fixed pin 127 in such a way that manual movement of the frame 102from right to left compresses the spring 129, which stores energy forsubsequent letter spacing. An idler gear 130 is mounted for rotationabout a pin 131 and engages the gear 128 and a gear 132. A toothed,

circular member 133 is integrally connected to and coaxial with gear132. Normally engaged with the circular, toothed member 133 is a dog135, which restrains the member 133 from clockwise motion due to theurging of the spring 129. The dog is slotted, and a fixed pin 136 passestherethrough. A spring 137 couples the dog 135 to a fixed pin 138 withthe tension of the spring 129 normally holding the lift side of the slotin the dog 135 against the pin 136. An L-shaped escapement member 139 ispivotably and slidably mounted on a fixed pin 141, and a slot in theescapement member 139 contains the pin 136. The width of the slot isgreater than the diameter of the pin 136 to permit the escapement member139 to pivot about the pin 141. The escapement member 139 is coupled tothe pin 138 by a spring 142, and the right side of the slot in member139 normally bears upon the pin 136- due to the tension of the spring142.

As previously described, the printing shell 80 is made to strike theplaten 89 by movement of the power bar 99 against the car on the bracket100. After printing the character, the frame must be moved to the nextletter space. Integrally connected to the power bar 99 is an arm 150which actuates the spacing mechanism in response to movement of thepower bar 99. A normally open contact assembly 152 is disposed above thearm 150 in a position where the contacts of the assembly 152 are closednear the limit of travel of the power bar 99 in its upwardly direction.The contacts of the assembly 152 machine by a spring 163 connected tothe post 164. It --follows that when the printing shell 80 approachesthe platen 89 the arm 150 attached to the power bar 99 closes thecontacts of the assembly 152 which applies voltage to the solenoid 154.The armature 156 is attracted pivoting the bell crank 158 clockwiseabout the pin 159 causing the rod 162 and the lower part of escapementmember 139 to move toward the rear of the machine. The escapevmentmember139 bears upon the dog 135 normally, and

when pivoted, disengages the dog 135 from the teeth in the circularmember 133; and at the same time, the escapement member 139 engages theteeth of the circular member 133. Since the circular member 133 is freeof the dog 135, it moves clockwise about the pin 142 moving theescapement member 139 to the right until the pin 136 rests against theleft side of the slot in the escapement member 139. Movement of thecircular, toothed member 133 causes the pulley 126 to turn advancing thetape 111 and the frame 102. For so long as the voltage is applied to thesolenoid 154, the escapement member 139 prevents the reentry of the doginto the teeth of the circular member 133 and restrains the toothedmember 133 from further motion. As the power bar 99 is. returning to itsrest and lower position, the contacts of the contact assembly 152 areopened de-energizing the solenoid 154. By urging of the spring 163, thebell crank 158 pivots counter-clockwise withdrawing the armature 156from the coil 154 and moving the rod 162 toward the front of themachine. The rod 162 pivots the escapement member 139 and moves theupper portion of the escapement member 139 out of engagement with theteeth on the circular member 133 and allows the dog 135 to become seatedin the next tooth of member 133. The dog 135 is urged to the right untilthe left side of the slot in the dog 135 comes to bear against the pin136 due to the clockwise motion of the toothed member 133; thereafter,the toothed member 133 is prevented from moving by the dog 135. Theescapement member 139 moves to the left by urging of the spring untilreturned to rest position. This completes one cycle of the spacingoperation to move the frame 102 one unit to the right.

Since the frame 102 carrying the printing head 80 moves longitudinallyalong the platen 89, it becomes necessary to adjust the tape controlsystem for this movement in order that there be no spurious motion ofthe pulleys 54 and 64. This is accomplished by sliding the member 58along the bar 59 as the frame 102 moves laterally, said sliding member58 moving in the direction opposite the travel of the frame 102. A tapeconnects to the sliding member 58, passes around a pulley 172 rotatableabout the fixed pin 173, passes around a pulley 174 rotatable about apin 175, connects to the frame 102, passes around a pulley 176 rotatableabout a pin 177, passes about a pulley 1'78 rotatable about a pin 179,and connects to the slidable member 58. Thus, movement of the frame 102to the right causes the same magnitude of movement of the sliding member58 in the opposite direction causing the tapes 56 and 66 to have noeffect on the tilt pulley 54 and the rotation pulley 64 during spacingoperations.

Should a second key lever 10 be depressed before the completion of theprinting cycle begun by the operation of the first key lever 10, theearlier printing cycle will not be interrupted. In Fig. 4, firstinterposer 11 has been engaged by the activating bail 31 and operationof the second key lever 10 causes its respective bell crank 14 to engageits respective interposer 11, but the movement of the activating bail 31past the shoulder of the second interposer 11 prevents said secondinterposer 11 from engaging normally. The second interposer 11 merelyrides on the top of the activating bail 31. The loosely pivoted end ofsecond interposer 11 is free to move downward and relieve the stresscaused by said second interposer 11 when it rides upon the activatingbail 31. A short time before the activating bail 31 returns to itsextreme clockwise position on the return stroke, the second interposer11 drops, operates the rod 18 which closes contact 23, and assumes aposition whereby it may engage with the activating bail 31. Closing thecontact 23 starts the reciprocating motion of the activating bail 31,second interposer 11 engages the activating bail 31, and the secondprinting cycle begins. This, in effect, stores the second key depressionuntil recovery of the selecting mechanism from the first key depression.

It will be noted that there is shown in Fig. 5 a mechanism for returningthe arm 34 to its home position. A like mechanism (not shown) isprovided for the arm '41. An arm 180 is mounted for rotation about afixed pin 181; likewise, an arm 182 is mounted for rotation about afixed pin 183. Both of the arms 1%, 182 bear upon a fixed stud 184,which is connected to the arm 34. A spring 186 is attached to each arm180 and 182 and resiliently holds the arms against the fixed pins 187and 188 respectively. With this arrangement of parts, swinging of thearm 34 clockwise causes the stud 184 to pivot the arm 182 clockwiseabout the pin 183. The arm 180 is prevented from clockwise movement bythe fixed pin 187, and the spring 186 is extended according to themovement of the arm 182. When the interposer has been withdrawn from thebar 32, the spring 186 causes the arm 182 to pivot counter-clockwiseacting upon the stud 184 to return the arm 34 to the rest position forproper alignment of the printing shell 80.

While there has been shown and described and pointed out the fundamentalnovel features of the invention as applied to the preferred embodiment,it will be understood that various omissions and substitutions andchanges in the form and details of the apparatus illustrated and in itsoperation may be made by those skilled in the art, without departingfrom the spirit of the invention. Therefore, it is the intention to belimited only as indicated by the scope of the following claims.

What is claimed is:

1. In a typewriter having a single element printing head with aplurality of characters thereon, a selecting mechanism for locating onecharacter at a time at a reference position comprising, in combination,positioning means for tilting and rotating the printing head, a pair ofmembers having cam portions constructed and arranged to displace saidpositioning means by predetermined increments, a plurality of actuatingelements pivotally and slidably mounted each assigned to one of thecharacters on the printing head and each actuable to position said cammembers according to the character selected, a bail mounted toreciprocate and slide said actuating elements when pivoted, power meansoperable to drive said bail, and key lever means adapted to pivot saidactuating elements and activate said power means.

2. In a typewriter having a single element printing head with aplurality of characters thereon, a selecting mechanism for locating onecharacter at a time at a reference position comprising, in combination,control means for tilting and rotating said printing head, positionableselection bars having recesses therein operable to actuate said controlmeans, a plurality of actuating elements pivotally and slidably mountedeach related to a character on the printing head and each actuable whenpivoted to engage the selection bars at said recesses therein toposition said bars, a bail operable to reciprocate and slide saidactuating elements, power means activated when the selected interposeris pivoted to drive said bail, a plurality of operable key levers, andmeans responsive to the operation of said key levers for pivoting saidactuating elements.

3. In a typewriter having an single element printing head with aplurality of characters thereon, a selecting mechanism for locating onecharacter at a time at a reference position comprising, in combination,positioning means including a flexible strand and a plurality of pulleysarranged to tilt and rotate the printing head, a pair of selecting barshaving a plurality of operating surfaces thereon mounted for lateralmovement to actuate said positioning means, said operating surfacesbeing inclined with respect to the direction of lateral movement of saidselecting bars, a plurality of interposers pivotally and slidablymounted each related to a character on the printing head and eachengageable with the selecting bars at particular inclined surfacesthereon to position said bars laterally according to the characterselected, a bail mounted to reciprocate effective to slide saidinterposers when said interposers are pivoted, power means for drivingsaid bail responsive when one of said interposers is pivoted, aplurality of bell cranks engageable with the actuating elements eachoperable to pivot its respective interposer and actuate the power means,and a plurality of pivotable key levers coupled to the bell cranks tooperate said bell cranks when one of said key levers is pivoted.

4. A claim in accordance with claim 3 wherein a bell crank pivotallymounted on one of said key levers is engageable with one of saidinterposers to pivot the latter when said key lever is pivoted, saidbell crank being engageable with said interposer to pivot said bellcrank when said interposer has been released from the bail therebypreventing repeated cycles from a single operation of said key lever.

5. In a typewriter including a printing member having a plurality ofcharacters thereon, a selecting mechanism for locating one character ata time at a reference posi tion comprising, in combination, positioningmeans for manipulating said printing member, selecting means includingcam elements adapted to operate said positioning means according to thecharacter selected, a plurality of actuating elements operable to engagethe cam elements of said selecting means, a bail mounted to reciprocatefor driving said actuating elements, power means for operating saidbail, and means including a plurality of key levers adapted to move froma rest position to an actuating position and return, to operaterespective actuating elements and to activate said power means, and uponmovement of respective actuating elements to be ineffective untilreturned to the rest position.

6. In a typewriter having a single element printing head with aplurality of characters thereon, a selecting mechanism for locating onecharacter at a time at a reference position comprising, in combination,positioning means including a flexible strand and at least one pulleyconstructed and arranged to tilt and rotate said printing head, a pairof differential bars adapted for lateral movement having inclinedportions at angles related to lateral distances for operating saidpositioning means by predetermined increments, a plurality ofinterposers pivotally and slidably mounted, each engageable with theditferential bars at particular inclined portions thereon to positionsaid differential bars according to the character selected, a pivotallymounted bail effective to slide said interposers when said interposersare pivoted, power means operable to drive said bail, a plurality ofmanipulatable key levers each associated with one of said interposers,and means coupled to said key levers for pivoting said interposers whensaid key levers are manipulated and activating said power means.

7. In a typewriter including a printing member having a plurality ofcharacters thereon, a selecting mechanism for locating one character ata time at a reference position comprising, in combination, positioningmeans for manipulating said printing member, selecting means includingcam elements adapted to operate said positioning means according to thecharacter selected, a plurality of actuating elements operable to engagethe cam elements of said selecting means, a bail mounted to reciprocatefor driving said actuating elements, power means for operating saidbail, and means including a plurality of key levers adapted to operatesaid actuating elements and to activate said power means, said bailoperating when reciprocated to block all of the other interposersagainst being driven until completion of the selection cycle andthereafter permit a different and previously selected actuating elementto be driven by said bail.

References Cited inthe file of this patent UNITED STATES PATENTS

